I am frugal - some would say "cheap". After buying a dozen plastic boxes and listening to my wallet whine, I got the inspiration to go dumpster-diving at the range and rescued a bunch of empty boxes.
I slit them at the seam, turned them inside out, then glued and taped the seam back up. I had some old address labels I print on the computer and use to tag the ammo.

I store my ammo in an old wall cabinet I made for VHS tapes way back when. It hadn't been used in a decade and was gathering dust in the basement so I "repurposed" it.